It is easily recognized that firearms are extremely and inherently dangerous. Little can be done to minimize their hazard without impairing their effectiveness. Besides cautious use, the firearm safety is practically the only means of preventing accidental discharge of the weapon.
In its most common form the safety is a mechanical latch or button, which in one position blocks the movement of the trigger and keeps the firearm from operating. Usually the position of the latch or button indicates to the user whether the weapon can be fired. However, this indication is less than positive and certain. Consequently, a person who is not familiar with the weapon may not know the position which indicates that the safety is effective. Thus, someone using a new gun or someone accompanying another person who has a gun, may not be fully aware of whether the safety is on or off. If the safety is off, the firearm may be accidentally discharged if the firearm strikes against some solid object, thus injuring the user or someone with him.
It would be a significant advance in weapon safety if a positive and unambiguous indication were provided when the safety was off and the weapon could be fired. Thus the user would know for sure when the safety was off if he looked at the indicator and would even be drawn to note the condition of the safety.